I agree buy scsi. Read after write is best.
The lower priced tr4 scsi drives don't have read after write. The seagate
scsi 8gb is $229 and has no read-after-write
I dont believe the colorado's do either.
A QIC tape has 40+ tracks recorded in serpentine fashion. This means it
records a track in the forward direction
then moves the head and records in the reverse direction. So each section of
tape is rubbed past the head 40 times.
If you verify then 80 times.
With 4mm DAT you start at the beginning and write until the end in 1 pass.
If you verify then 2.
If you have a damaged section of tape, (worn or crinkled) then the drive has
to try to read that section 40 times.
If the drive or software do retries then it may reread weak sections of tape
640 times. Each retry wears the tape out
a little more.
Most QIC tapes are designed with a belt which physically presses against the
recorded surface of the tape the
entire time. This belt is also prone to problems. If you open the tape door
on a cartirdge you can see the
creases down the middle of the tape from the belt.
DAT tapes cost about $10-12.
TR4 is $26+.
QIC tapes are preformatted. There is a map at the beginning of the tape
which says, segments x,y,and z are bad
so don't write there. If new defects develop then they will not be detected
until you verify the tape. Verifying
requires a separate pass and is often skipped. So many users don't find out
about the unreadable tape until
you need to restore.
DAT tapes are formatted on the fly as the data is being backed-up. There is
immediate read-after-write verification
occuring as the data is written. If it is unreadable then the drive keeps
rewriting the data until it passes the bad area
or it gives up (typically after 16 attempts) alerting you to the problem.
I don't know much about the new NS8 and AIT drives. I know the NS8 has
read-after-write.
DAT is more expensive. But you'll save in the long run in the price of the
cartridges. You will save over $100
buying 10 tapes. There are plenty of 4mm DAT's for $600.
Martin Jacobs wrote:
> Hello Gavin,
>
> > ...
> > I have about a Five Hundred Dollars US to spend on a tape backup drive
> > SCSI or non SCSI, what would you recommend that is stable with the 2.2
> > kernels?
> > ...
>
> If you can, buy an SCSI tape. They are fast, you should not have
> to deal with drivers and questions like that and the most have
> hardware compression and read-after-write verification.
>
> I for myself would prefer a non-DAT drive because QIC-tapes are
> more robust. But thats more a question of taste.
>
> Martin
>
> --
> Martin Jacobs * Windsbach * [EMAIL PROTECTED] und
> [EMAIL PROTECTED]
> Registered Linux User #87175
